It is common to apply submersible pumps for pumping away waste water containing solid matter. These pumps as a rule are provided with a single-channel or multi-channel impeller for delivering waste water. Such a submersible pump is known for example from EP 1 300 594 B1. The pump described there, on the entry side of its impeller in the region of the suction port comprises a cutting device which fragments or reduces the size of the solid matter contained in the waste water to be delivered, in order to prevent a blockage of the pump impeller. As a rule, the waste water delivery with this pump has been found to be unproblematic. However, the fragmented solid matter constituents as well as the air sucked by the pump can penetrate into the comparatively large cavity of the impeller and thus lead to vibrations and flow noise resulting therefrom. Such cavities with single-channel impellers result on the rear side of the flow channel in the inside of the impeller and are usually open to the axial end of the impeller which is away from the suction port. The solid particles located in the cavity of the impeller also represent a problem with regard to the shaft seal which seals the pump housing with respect to the drive shaft of the impeller which is led into the pump housing, since if these solid particles get into the shaft seal, they can negatively influence its functional characteristics and cooling as the case may be.